Which children are underweight?

These are children who have a body weight for their age that is below the 3rd centile. Therefore, they weigh less than the normal range for their age. Many have been underweight for months or years while others have only recently lost weight. Malnutrition should be considered in all underweight children. There are, however, many causes of being underweight other than malnutrition (e.g. being born preterm).